U.S. patent application number 13/770480 was filed with the patent office on 2013-06-20 for photovoltaic module.
The applicant listed for this patent is Gregory F. Jacobs, Husnu M. Kalkanoglu, Ming Liang Shiao. Invention is credited to Gregory F. Jacobs, Husnu M. Kalkanoglu, Ming Liang Shiao.
Application Number | 20130153009 13/770480 |
Document ID | / |
Family ID | 40853738 |
Filed Date | 2013-06-20 |
United States Patent
Application |
20130153009 |
Kind Code |
A1 |
Kalkanoglu; Husnu M. ; et
al. |
June 20, 2013 |
PHOTOVOLTAIC MODULE
Abstract
A photovoltaic module includes an encapsulated photovoltaic
element and an infrared-transmissive decorative overlay simulating
conventional roofing.
Inventors: |
Kalkanoglu; Husnu M.;
(Swarthmore, PA) ; Jacobs; Gregory F.; (Oreland,
PA) ; Shiao; Ming Liang; (Collegeville, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kalkanoglu; Husnu M.
Jacobs; Gregory F.
Shiao; Ming Liang |
Swarthmore
Oreland
Collegeville |
PA
PA
PA |
US
US
US |
|
|
Family ID: |
40853738 |
Appl. No.: |
13/770480 |
Filed: |
February 19, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12811493 |
Jul 1, 2010 |
8404967 |
|
|
PCT/US09/30253 |
Jan 7, 2009 |
|
|
|
13770480 |
|
|
|
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61019740 |
Jan 8, 2008 |
|
|
|
Current U.S.
Class: |
136/251 ;
136/256; 438/64 |
Current CPC
Class: |
H01L 31/18 20130101;
H01L 31/02 20130101; H01L 31/0203 20130101; H02S 20/23 20141201;
H01L 31/02168 20130101; H02S 40/20 20141201; Y02E 10/50 20130101;
B32B 17/10788 20130101; H01L 31/048 20130101; H02S 20/25 20141201;
Y02B 10/10 20130101 |
Class at
Publication: |
136/251 ;
136/256; 438/64 |
International
Class: |
H01L 31/0216 20060101
H01L031/0216; H01L 31/18 20060101 H01L031/18 |
Claims
1. A photovoltaic module comprising a photovoltaic element having
an upper surface, an encapsulant resin layer over the upper surface
of the photovoltaic element, and a decorative overlay positioned
above the upper surface of the photovoltaic element, the overlay
being substantially transmissive of near infrared radiation and
infrared radiation.
2. A photovoltaic module according to claim 1 wherein the
decorative overlay is positioned outside the encapsulant resin
layer.
3. A photovoltaic module according to claim 1 wherein the
decorative overlay is positioned under the encapsulant resin
layer.
4. A photovoltaic module according to claim 1 wherein the
decorative overlay simulates the appearance of a conventional
roofing shingle surface.
5. A photovoltaic module according to claim 1 wherein the
decorative overlay comprises a coating layer including a binder and
at least one infrared-transmissive pigment.
6. A photovoltaic module according to claim 5 wherein the at least
one infrared-transmissive pigment is selected from the group
consisting of zinc sulfide, zinc oxide, nanoparticle titanium
dioxide, CI Pigment Black 31, CI Pigment Black 32, CI Pigment Red
122, and CI Pigment Yellow 13
7. A photovoltaic module according to claim 1 wherein the overlay
comprises a film material.
8. A photovoltaic module according to claim 6 wherein the film
material includes a carrier and at least one infrared-transmissive
pigment.
9. A photovoltaic module according to claim 7 wherein the film
material includes a decorative layer on the surface of the
film.
10. A photovoltaic module according to claim 9 wherein the
decorative layer is formed by a halftone printing process.
11. A process for producing a decorative photovoltaic module
comprising: (a) providing a photovoltaic module including a
semiconductor stack encapsulated in an infrared-transmissive resin
having an upper resin layer, and (b) adhering an overlay film
bearing a decorative pattern to the upper resin layer using an
infrared-transmissive adhesive material.
12. The process of claim 11, wherein the decorative pattern further
includes an infrared-transmissive ink on at least a first portion
of the upper resin layer and an opaque ink on at least a second
portion of the upper resin layer.
13. The process of claim 11, wherein the decorative photovoltaic
module is incorporated into a roofing cover.
14. A process for producing a decorative photovoltaic module
comprising: (a) providing a photovoltaic element including a
semiconductor stack, the photovoltaic element having an upper
surface, (b) providing a decorative overlay positioned above the
upper surface of the photovoltaic element, the overlay being
substantially transmissive of near infrared radiation and infrared
radiation, and (c) encapsulating the decorative overlay and the
photovoltaic element in an infrared-transmissive resin.
15. A process according to claim 14 wherein the decorative overlay
simulates the appearance of a conventional roofing shingle
surface.
16. A process according to claim 15 wherein the decorative overlay
comprises a coating layer including a binder and at least one
infrared-transmissive pigment.
17. A process according to claim 14 wherein the overlay comprises a
film material.
18. A process according to claim 17 wherein the film material
includes a decorative layer on the surface of the film.
19. A process according to claim 18 wherein the decorative layer is
formed by a halftone printing process.
20. A process according to claim 14 wherein (a) the photovoltaic
element is encapsulated in an infrared-transmissive resin, (b) the
decorative overlay is positioned above the upper surface of the
encapsulated photovoltaic element, and (c) the decorative overlay
is encapsulated in an infrared-transmissive resin.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of pending U.S. patent application
Ser. No. 12/811,493, filed on Jul. 1, 2010, which is a national
stage 371 application of International Application No.
PCT/US2009/030253, filed Jan. 7, 2009, which claims the benefit of
U.S. Provisional Patent Application No. 61/019740, filed Jan. 8,
2008.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to photovoltaic modules, and
in particular to photovoltaic modules adapted for installation on
roofs.
[0004] 2. Brief Description of the Prior Art
[0005] The use of photovoltaic ("PV") modules on roofs is becoming
increasingly common. Often perched on tile or shingle-covered
roofs, these solar energy-generating arrays are quite visible, and
generally not quite aesthetically pleasing to the eye, somewhat
comparable to the TV antennas of the past. To date the
installations appear to have been motivated by purely practical,
functional considerations; there generally appears to be little to
no color and design coordination between the PV modules and the
roofing tiles or shingles on which the modules are mounted.
[0006] PV modules usually feature a black to purple or blue surface
protected by a thin transparent glass or plastic cover. These
colors frequently do not work well aesthetically with the rest of
the roof.
[0007] Photovoltaic materials require incident light to produce
energy via the photoelectric effect. Such materials typically have
a wavelength dependency in their response to incident light. That
is to say that some parts of the spectrum may be used by a PV
module more effectively than others in producing electricity.
Intuitively, to cover or color the PV module with an opaque
material to obtain a desirable aesthetic appearance would cause a
blocking of the incident light and the photovoltaic material would
no longer be active. To color the top surface with a clear coating,
film or membrane may change the color, but may not easily yield a
desirable effect for a roofing product. Also, a visually
transparent film may still block parts of the spectrum important
for power generation.
[0008] A variety of approaches have been taken for using the
substantial area provided by roofs to collect solar energy. One
approach has been to cover existing roofs using systems employing
panels, tiles or shingles including solar cells. Panel-type systems
are disclosed, for example, in U.S. Pat. No. 5,232,518 and U.S.
Pat. No. 6,245,987.
[0009] Various attempts have been made to blend photovoltaic cells
with traditional roofing systems. For example, U.S. Pat. Nos.
5,437,735 and 5,575,861, each incorporated herein by reference,
disclose a photovoltaic shingle system including a strip of roofing
material having an overlap portion, and tabs extending from the
overlap portion. Each of the tabs includes a photovoltaic device.
U.S. Pat. No. 6,875,914 discloses a photovoltaic roofing system
including photovoltaic power-generating roofing shingles provided
with a linearly aligned electrical terminal. A protective cap
shields the electrical connections. U.S. Pat. No. 6,883,290
discloses a shingle system including photovoltaic modules secured
to a base to create a shingle assembly with a venting region
between the module and the base for temperature regulation. U.S.
Pat. No. 6,928,775 discloses a multi-use electric tile module for
walling, flooring or roofing applications that can include a
photovoltaic module. U.S. Patent Application Publication No.
2006/0000178 discloses a shingle assembly with a support bracket
specifically adapted for the installation of photovoltaic
shingles.
[0010] U.S. Pat. No. 4,574,160 discloses a flexible, rollable
photovoltaic cell module. U.S. Pat. No. 4,860,509 discloses
photovoltaic cells in combination with single-ply roofing
membranes.
[0011] U.S. Patent Application Publication No. 2005/0102947
discloses photovoltaic building materials having a regular shape,
such as rectangular or trapezoidal, and carrying solar cells formed
from thin film materials, conventional crystal/silica, or
photoelectric silica spheres. The materials are specially adapted
for installation along the ridgeline of a roof. U.S. Patent
Application Publication No. 2005/0144870 discloses a shingle system
incorporating a photovoltaic module and a base to define a venting
region, and may include a waterproofing element.
[0012] U.S. Patent Application Publication No. 2005/0178429
discloses flexible integrated photovoltaic roofing membrane
shingles having a "dragon's tooth" shape with solar elements that
connect electrically with previous and successive shingle courses.
U.S. Patent Application Publication No. 2005/0263179 discloses a
photovoltaic module architecture which includes electrical
interconnects that provide for connecting the anode of one module
with the cathode of another module.
[0013] U.S. Patent Application Publication No. 2005/0268962
discloses flexible photovoltaic cells and related systems. U.S.
Pat. No. 6,729,081, incorporated herein by reference, discloses a
self-adhesive photovoltaic module. U.S. Patent Application
Publication No. 2006/0032527 discloses a solar panel overlay and
assembly for mounting on an underlying roof deck, designed to mimic
the appearance of the underlying shingled roof deck.
[0014] U.S. Patent Application Publication No. 2003/0121228
discloses a dendritic web solar cell shingling system providing
much thinner photovoltaic arrays than conventional cells.
[0015] U.S. Pat. No. 6,730,841 discloses a method and apparatus for
mounting a flexible photovoltaic roofing material.
[0016] U.S. Patent Application Publication No. 2006/0042683
discloses a system for mounting photovoltaic cells on a surface and
for using the electrical energy produced. The cell can be pigmented
to assure efficient collection of available radiation, for example,
by using a pink-colored glass.
[0017] U.S. Patent Application Publication No. 2005/0048821
discloses a dye-sensitized solar cell having a high conversion
efficiency.
[0018] U.S. Patent Application Publication No. 2003/0154973
discloses a radiation collector configured to collect incident
radiation. The collectors can be colored to give the appearance of
traditional shingles or other roofing or building material such
that the roof appears aesthetically the same as a traditional
roof.
[0019] U.S. Pat. No. 5,650,019 discloses a solar cell module having
a three-layer structure including a thin film solar cell, a hard
resin layer such as polycarbonate to mechanically protect the solar
cell, an ultraviolet radiation absorbing adhesive layer to protect
the hard resin layer, such as ethylene vinyl acetate including an
ultraviolet absorber such as a suitable benzophenone or triazole,
and an outermost layer having excellent weatherability, such as a
fluororesin.
[0020] U.S. Pat. No. 6,331,673 discloses an amorphous silicon solar
cell module in which the solar cell is encapsulated in a
transparent organic polymer, namely an acrylic resin and covered
with a thin film of a suitable fluoropolymer resin, reinforced with
glass fibers.
[0021] There is a continuing need for photovoltaic modules having
more controllable and desirable aesthetics for use in roof
applications while still maintaining sufficient efficiency in power
generation.
SUMMARY OF THE INVENTION
[0022] The present invention provides a photovoltaic module
comprising a photovoltaic element having an upper surface, an
encapsulant resin layer over the upper surface of the photovoltaic
element, a decorative overlay positioned above the upper surface of
the photovoltaic element, and an optional cover plate. The
decorative overlay is preferably substantially transmissive of both
near infrared radiation and infrared radiation.
[0023] Preferably, the decorative overlay is selected so that the
operation of the photovoltaic element is not substantially
inhibited. Preferably, the electrical power output from the
photovoltaic element is not substantially reduced by the presence
of the decorative overlay.
[0024] In one presently preferred embodiment of the present
invention, the decorative overlay is positioned outside the
optional cover plate. In another embodiment of the present
invention, the decorative overlay is positioned under the optional
cover plate. In a further embodiment of the present invention, the
decorative overlay is embedded in the encapsulant resin layer. In
yet another embodiment of the present invention, the decorative
overlay is positioned on top of the encapsulant resin layer.
[0025] Preferably, in one aspect the present invention provides a
photovoltaic module wherein the decorative overlay simulates the
appearance of a conventional roofing shingle surface. In another
aspect, the present invention provides a photovoltaic module
wherein the decorative overlay simulates the appearance of a clay
ceramic or cementitious roofing tile. In yet another aspect, the
present invention provides a photovoltaic module wherein the
decorative overlay simulates the appearance of a polymeric roofing
or siding panel.
[0026] The decorative overlay can be provided in a number of
different ways. For example, in one aspect, the decorative overlay
comprises a coating layer or ink including a binder and at least
one infrared-transmissive pigment. The coating layer or ink can be
applied directly to the optional cover plate of the photovoltaic
module, directly on the encapsulant resin layer, or on an
infrared-transmissive film. Preferably, the at least one
infrared-transmissive pigment is selected from the group consisting
of nanoparticle titanium dioxide, zinc sulfide, zinc oxide, CI
Pigment Black 31, CI Pigment Black 32, CI Pigment Red 122, and CI
Pigment Yellow 13. Thus, the decorative overlay can comprise a film
material. In one aspect, the film material includes a carrier and
at least one infrared-transmissive pigment. In another aspect, the
film material includes a decorative layer formed on the surface of
the film. When the decorative layer is printed on the film
material, the encapsulant resin layer, or the optional cover plate,
the decorative layer is preferably formed by a halftone printing
process.
[0027] The present invention also provides a process for producing
a decorative photovoltaic module. In one embodiment, the process
includes providing a photovoltaic module including a semiconductor
stack encapsulated in an infrared-transmissive resin to form an
encapsulant resin layer and optionally covered with a top plate,
and adhering an overlay film bearing a decorative pattern to the
encapsulant resin layer or optional top plate using an
infrared-transmissive adhesive material. In another embodiment, the
process of the present invention comprises providing a photovoltaic
module including a semiconductor stack encapsulated in an
infrared-transmissive resin to form an encapsulant resin layer and
covered with an optional top plate, and printing a decorative
pattern on the encapsulant resin layer or optional top plate using
an infrared-transmissive ink. In a further embodiment of the
process of the present invention, the process comprises providing a
photovoltaic module including a semiconductor stack encapsulated in
a layer of an infrared-transmissive resin to form an encapsulant
resin layer, adhering an overlay film bearing a decorative pattern
to the layer of infrared-transmissive resin, and optionally
adhering a top plate to the overlay film using an
infrared-transmissive adhesive material.
[0028] In another aspect, the present invention provides a
photovoltaic module comprising a photovoltaic element having an
upper surface, an encapsulant resin layer over the upper surface of
the photovoltaic element, and a decorative overlay positioned above
the upper surface of the photovoltaic element. In this aspect, the
overlay is substantially transmissive of near infrared radiation
and infrared radiation. In this aspect, the decorative overlay can
be positioned outside the encapsulant resin layer, under the
encapsulant resin layer, or the decorative overlay can be embedded
in the encapsulant resin layer. Preferably, the decorative overlay
simulates the appearance of a conventional roofing shingle surface,
a conventional roofing tile or slate, or a conventional metal or
polymeric roofing panel or siding panel.
[0029] In this aspect, the decorative overlay preferably comprises
a coating layer including a binder and at least one
infrared-transmissive pigment. Preferably, the at least one
infrared-transmissive pigment is selected from the group consisting
of zinc sulfide, zinc oxide, nanoparticle titanium dioxide, CI
Pigment Black 31, CI Pigment Black 32, CI Pigment Red 122, and CI
Pigment Yellow 13. Preferably, the overlay comprises a film
material. Preferably, the film material includes a carrier and at
least one infrared-transmissive pigment. Preferably, the film
material includes a decorative layer on the surface of the film. In
one embodiment of the photovoltaic module of the present invention,
the decorative layer is preferably formed by a halftone printing
process.
[0030] In yet another aspect, the present invention provides a
process for producing a decorative photovoltaic module comprising
providing a photovoltaic module including a semiconductor stack
encapsulated in an infrared-transmissive resin having an upper
resin layer, and adhering an overlay film bearing a decorative
pattern to the upper resin layer using an infrared-transmissive
adhesive material. Preferably, the decorative photovoltaic module
is incorporated into a roofing cover.
[0031] In another aspect, the present invention provides a process
for producing a decorative photovoltaic module comprising providing
a photovoltaic module including a semiconductor stack encapsulated
in an infrared-transmissive resin having an upper resin layer, and
printing a decorative pattern on the upper resin layer using an ink
selected from the group consisting of opaque inks,
infrared-transmissive inks and partially transmissive inks.
Preferably, the decorative pattern further includes an
infrared-transmissive ink on at least a first portion of the upper
resin layer and an opaque ink on at least a second portion of the
upper resin layer. In one aspect of the present process, the
decorative photovoltaic module is preferably incorporated into a
roofing cover.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is schematic plan view showing a process for
producing a photovoltaic module according to the present invention
and employing an infrared-transmissive overlay film and a
conventional photovoltaic cell.
[0033] FIG. 2 is a schematic plan view showing the process of FIG.
1, substituting an overlay film having a mottled appearance in the
visible range but being substantially transmissive to near infrared
and infrared radiation.
[0034] FIG. 3 is a schematic plan view showing a second process for
producing a modified photovoltaic module according to the present
invention, in which a design is printed on a conventional
photovoltaic module using a four-color technique with ink pigmented
to be absorbed in the visible range, but substantially transmissive
to near infrared and infrared radiation, and optionally leaving
some areas of the surface without color printed on the module.
[0035] FIG. 4 is a schematic sectional elevational view of a
photovoltaic module of the prior art.
[0036] FIG. 5 is a schematic sectional elevational view of a first
embodiment of a photovoltaic module of the present invention.
[0037] FIG. 6 is a schematic sectional elevational view of a second
embodiment of a photovoltaic module of the present invention.
[0038] FIG. 7 is a schematic sectional elevational view of a third
embodiment of a photovoltaic module of the present invention.
[0039] FIG. 8 is a schematic sectional elevational view of a fourth
embodiment of a photovoltaic module of the present invention.
[0040] FIG. 9 is a schematic sectional elevational view of a fifth
embodiment of a photovoltaic module of the present invention.
[0041] FIG. 10 is a schematic sectional elevational view of a sixth
embodiment of a photovoltaic module of the present invention.
[0042] FIG. 11 is a schematic sectional elevational view of a
seventh embodiment of a photovoltaic module of the present
invention.
[0043] FIG. 12 is a schematic sectional elevational view of an
eighth embodiment of a photovoltaic module of the present
invention.
DETAILED DESCRIPTION
[0044] As used in the present specification and claims:
[0045] "Photovoltaic module" means one or more photovoltaic cells
electrically connected to operate as an integral unit.
[0046] "Infrared radiation" means electromagnetic radiation having
a wavelength of from 1.4 micrometers to 1000 micrometers.
[0047] "Near infrared radiation" means electromagnetic radiation
having a wavelength of from 0.75 micrometers to 1.4
micrometers.
[0048] "Visible radiation" means electromagnetic radiation having a
wavelength of from 350 to 750 nanometers.
[0049] "Substantially transmissive" when referring to radiation
means having an average transmission coefficient of at least 50
percent.
[0050] "Highly transmissive" when referring to radiation means
having an average transmission coefficient of at least 80
percent.
[0051] In one aspect, the present invention provides improved
photovoltaic modules having surface colors that are aesthetically
compatible with other types of roof coverings, such as previously
installed shingles, tiles, slate, etc.
[0052] Solar radiation has substantial spectral components in the
near infrared and infrared ranges. Preferably, the photovoltaic
modules of the present invention include a color layer that is
formulated to be substantially transmissive or transparent to the
infrared portion of the spectrum, thus to permit photovoltaic
modules to function while using the visible portion of the spectrum
to achieve a desired aesthetic effect.
[0053] Conventional solar cells can include several layers, such as
an n-type silicon layer doped with an electron donor such as
phosphorous, oriented towards incident solar radiation, and a
p-type silicon layer doped with an electron acceptor, such as
boron, as well as a pair of electrical current conducting layers
for interconnection with other cells and/or the environment. The
silicon layers can be embedded in a protective layer of encapsulant
material, such as ethylene vinyl acetate, and covered with glass.
Antireflection coatings can be applied to the electron-donor layer
and the glass to maximize solar radiation adsorption. The
antireflection coating gives the conventional solar cell a
characteristic blue or black appearance.
[0054] The present invention provides a photovoltaic module having
controllable and desirable aesthetics for use in roof applications
while still maintaining sufficient efficiency in power generation.
The photovoltaic device of the present invention is provided with a
coating or overlay layer having a desirable visual appearance in
the visible spectrum and substantial transmissivity in the near
infrared and infrared regions of the electromagnetic spectrum.
Portions of the visible spectrum are selectively absorbed so that
the light reflected in the visible range gives a desired color
while the near infrared and infrared light, or at least a
substantial portion thereof, passes through the coating or overlay
to activate the photovoltaic device.
[0055] Referring now to the figures in which like reference
numerals represent like elements in each of the several views,
there is shown in FIG. 1 a schematic plan view of a process for
producing a modified photovoltaic module 1c according to the
present invention and employing an infrared transparent overlay
film 1b and a conventional photovoltaic module 1a including a
mono-crystalline silicon solar cell covered with a dark blue
silicon nitride antireflection film and available from China
Electrical Equipment Group, Nanjing, China. In the present process
an overlay film 1b is placed over and adhered to the upper surface
of a conventional photovoltaic module 1a. The overlay film 1b is
transparent or transmissive for radiation in the infrared and
near-infrared portions of the spectrum, but includes a
visible-light absorbing pigment to provide a monochromatic
appearance to the human eye. The film 1b is bonded to the upper
surface of the conventional photovoltaic module 1a using an
infrared light-transmissive adhesive (not shown), such as an
ethylene vinyl acetate hot melt adhesive composition having a
softening point greater than the anticipated operating temperature
range for the modified photovoltaic module 1c. Alternatively, the
overlay film 1b can be placed over the conventional photovoltaic
module 1a and secured mechanically (not shown) to provide the
modified photovoltaic module 1c.
[0056] FIG. 2 depicts the process of FIG. 1, except that an overlay
film 2b having a mottled appearance is substituted for the
monochromatic overlay film 1b employed in the process of FIG. 1.
The overlay film 2b has a mottled appearance in the visible range
but is substantially transparent to near infrared and infrared
radiation. Application of the mottled overlay film 2b to a
conventional photovoltaic module 2a provides a modified
photovoltaic module 2c having a mottled appearance.
[0057] FIG. 3 depicts a further embodiment of a process for
producing a modified photovoltaic cell according to the present
invention. In this embodiment, infrared-transmissive ink or coating
material is applied directly to the copper nitride surface of the
conventional photovoltaic cell. Four different inks, each having a
different appearance in the visible spectrum, but each being
infrared and near-infrared-transmissive, are applied as a pattern
3b to the upper surface of a conventional photovoltaic module 3a
using a suitable technique, such as a lithographic or ink-jet
technique, to provide a modified photovoltaic module 3c. The
pattern can be a screened stochastic half-tone pattern reproducing
a color image, such as an image of a section of a conventional
roofing shingle covered with roofing granules colored with
conventional metal oxide colorants. For purposes of illustration,
the individual color "dots" forming the pattern are depicted as
being large enough to be individually distinguishable to the
unaided eye. However, a much finer screened pattern can be
employed, such as one having a frequency of 30-200 lines per inch,
to provide a conventional half-tone image. Optionally, one, two or
more different color inks or coating compositions can be used to
form the color "dots." Further, the pattern can exploit the
preexisting colors of the other components of the photovoltaic
module to achieve a desired aesthetic result.
[0058] A conventional photovoltaic module 10 of the prior art is
depicted in the schematic sectional elevational view of FIG. 4. The
photovoltaic module 10 includes a solar cell stack 12 formed from a
plurality of layers (not shown) including n-type and p-type
crystalline, polycrystalline or amorphous silicon layers,
transparent electrode layers, and a backing plate, and fitted with
external current collecting electrodes 14 for connecting the solar
cell stack to permit a photocurrent to flow from the solar cell
stack 12 to an external load (not shown). The solar cell stack 12
is encapsulated on its upper surface (the surface intended to face
the sun) by an outer layer of upper surface encapsulant resin 16,
and on its lower surface by an inner layer 20 of lower surface
encapsulant resin. The upper surface encapsulant resin is covered
with a cover or top plate 18 transparent or transmissive to
infrared and near infrared radiation such as a suitable glass sheet
or suitable fluororesin film, and the lower surface encapsulant
resin layer 20 is covered by a backing plate 22 formed from a rigid
material such as a rigid synthetic polymer composition such as a
nylon or polycarbonate or a metal such as aluminum.
[0059] A modified photovoltaic module 30 according to a first
embodiment of the present invention is schematically illustrated in
the sectional elevational view of FIG. 5. The modified photovoltaic
module 30 includes a solar cell stack 32 fitted with external
current collecting electrodes 34 for connecting the solar cell
stack 32 to an external load. The solar stack 32 is encapsulated on
its upper surface by an outer layer of upper surface encapsulant
resin 36, and on its lower surface by an inner layer 40 of lower
surface encapsulant resin. The upper surface encapsulant resin
layer 36 is covered with a top plate 38, and the lower surface
encapsulant resin layer 36 is covered by a backing plate 44. The
upper surface encapsulant resin layer 36 and the lower surface
encapsulant resin layer 40 can be formed from the same resin
material, or they can be formed from different resin materials.
However, the upper surface encapsulant resin layer 36 is preferably
formed from a resin material that is substantially transparent or
transmissive to both near infrared radiation and infrared
radiation, such as an ethylene vinyl acetate resin. An
infrared-transmissive overlay film 46 is adhered to the upper or
outer surface of the top plate 38 by a thin film 48 of
infrared-transmissive adhesive material. Optionally, the
infrared-transmissive overlay film 46 may itself be adherable
without the need for an additional thin film adhesive 48 (not
shown). The overlay film 46 includes a surface coating 49 including
pigment-absorbing radiation in the visible range arranged in a
decorative pattern, such as illustrated in FIG. 3b. Surface coating
49 can optionally be applied directly to top plate 38 (also not
shown).
[0060] A modified photovoltaic module 50 according to a second
embodiment of the present invention is schematically illustrated in
the sectional elevational view of FIG. 6. As in the case of the
first embodiment of the modified photovoltaic module 30 illustrated
in FIG. 5, the modified photovoltaic module 50 of this second
embodiment includes a solar cell stack 52 fitted with external
current collecting electrodes 54 for connecting the solar cell
stack 52 to an external load. Further, the solar stack 52 is
encapsulated on its upper surface by an outer layer of upper
surface encapsulant resin 56, and on its lower surface by an inner
layer 60 of lower surface encapsulant resin. In addition, the lower
surface encapsulant resin layer 60 is covered by a backing plate
64. However, in this case, the upper surface encapsulant resin
layer 56 is covered with an infrared-transmissive overlay film 66,
which in turn is covered by a top plate 58. In this case, the
infrared-transmissive overlay film 66 includes pigment-absorbing
radiation in the visible range, dispersed in the overlay film 66 to
give a mottled appearance to the overlay film 66, such as
illustrated in FIG. 1b. The top plate 58 is adhered to the overlay
film 66 by a thin film 68 of infrared-transmissive adhesive
material.
[0061] A modified photovoltaic module 70 according to a third
embodiment of the present invention is schematically illustrated in
the sectional elevational view of FIG. 7. As in the case of the
first embodiment of the modified photovoltaic module 30 illustrated
in FIG. 5, the modified photovoltaic module 70 of this third
embodiment includes a solar cell stack 72 fitted with external
current collecting electrodes 74 for connecting the solar cell
stack 72 to an external load. Further, the solar stack 72 is
encapsulated on its lower surface by an inner layer 80 of lower
surface encapsulant resin, and the lower surface encapsulant resin
layer 80 is covered by a backing plate 84. However, in this case,
the upper surface encapsulant resin layer 76 is formed from an
infrared-transmissive material including pigment absorbing
radiation in the visible range, dispersed randomly in the upper
encapsulant resin layer 76 to give a distinctive hue to the
encapsulant resin layer 76, the hue being selected to match or
complement the hue of a conventional roofing shingle. The upper
encapsulant layer 76 is in turn covered by a top plate 78.
[0062] A modified photovoltaic module 90 according to a fourth
embodiment of the present invention is schematically illustrated in
the sectional elevational view of FIG. 8.
[0063] As in the case of the first embodiment of the modified
photovoltaic module 30 illustrated in FIG. 5, the modified
photovoltaic module 90 of this fourth embodiment includes a solar
cell stack 92 fitted with external current-collecting electrodes 94
for connecting the solar cell stack 92 to an external load.
Further, the solar stack 92 is encapsulated on its upper surface by
an outer layer of upper surface encapsulant resin 96, and on its
lower surface by an inner layer 100 of lower surface encapsulant
resin. In addition, the upper surface encapsulant resin layer 96 is
covered with a top plate 98, and the lower surface encapsulant
resin layer 100 is covered by a backing plate 104. An
infrared-transmissive overlay film 106 is adhered to the upper or
outer surface of the top plate 98 by a thin film 108 of
infrared-transmissive adhesive material. In another embodiment, the
adhesive material is omitted, and the overlay film 108 is secured
otherwise, such by suitable fasteners or edging material (not
shown) to the top plate 98. The upper surface of the overlay film
106 is provided with a three-dimensional pattern simulating the
appearance of roofing granules on a conventional roofing shingle.
The three-dimensional pattern can be created by embossing, molding,
selectively coating, or by any of the many ways known in the art
for creating a three-dimensional pattern. In addition, the overlay
film 106 includes pigment-absorbing radiation in the visible range,
providing a hue simulating the hue of a conventional roofing
shingle.
[0064] A modified photovoltaic module 110 according to a fifth
embodiment of the present invention is schematically illustrated in
the sectional elevational view of FIG. 9. As in the case of the
first embodiment of the modified photovoltaic module 30 illustrated
in FIG. 5, the modified photovoltaic module 110 of this fifth
embodiment includes a solar cell stack 112 fitted with external
current collecting electrodes 114 for connecting the solar cell
stack 112 to an external load. The solar stack 112 is encapsulated
on its upper surface by an outer layer of upper surface encapsulant
resin 116, and on its lower surface by an inner layer 120 of lower
surface encapsulant resin. In addition, the lower surface
encapsulant resin layer 120 is covered by a backing plate 124. In
this embodiment of the present invention, the upper surface
encapsulant resin layer 116 is covered with an
infrared-transmissive overlay film 126. The lower surface of the
overlay film 126 is provided with a three-dimensional pattern
simulating the appearance of roofing granules on a conventional
roofing shingle. In addition, the overlay film 126 includes pigment
that absorbs radiation in the visible range, providing a hue
simulating the hue of a conventional roofing shingle. The upper
surface of the overlay film 126 is covered with a top plate 118,
and adhered to the lower surface of the top plate 118 by a thin
film 128 of infrared-transmissive adhesive material.
[0065] A modified photovoltaic module 130 according to a sixth
embodiment of the present invention is schematically illustrated in
the sectional elevational view of FIG. 10. As in the case of the
first embodiment of the modified photovoltaic module 30 illustrated
in FIG. 5, the modified photovoltaic module 130 of this sixth
embodiment includes a solar cell stack 132 fitted with external
current-collecting electrodes 134 for connecting the solar cell
stack 132 to an external load. Further, the solar stack 132 is
encapsulated on its upper surface by an outer layer of upper
surface encapsulant resin 136, and on its lower surface by an inner
layer 140 of lower surface encapsulant resin. In addition, the
upper surface encapsulant resin layer 136 is covered with a top
plate 138, and the lower surface encapsulant resin layer 140 is
covered by a backing plate 144. In this embodiment of the present
invention, an infrared-transmissive overlay film 146 is embedded in
the upper surface encapsulant resin layer 136. The overlay film 146
is provided with a three-dimensional pattern simulating the
appearance of roofing granules on a conventional roofing shingle.
In addition, the overlay film 146 includes pigment that absorbs
radiation in the visible range, providing a hue simulating the hue
of a conventional roofing shingle.
[0066] A modified photovoltaic module 150 according to a seventh
embodiment of the present invention is schematically illustrated in
the sectional elevational view of FIG. 11.
[0067] As in the case of the first embodiment of the modified
photovoltaic module 30 illustrated in FIG. 5, the modified
photovoltaic module 150 of this seventh embodiment includes a solar
cell stack 152 fitted with external current-collecting electrodes
154 for connecting the solar cell stack 152 to an external load.
Further, the solar stack 152 is encapsulated on its upper surface
by an outer layer of upper surface encapsulant resin 156, and on
its lower surface by an inner layer 160 of lower surface
encapsulant resin. In addition, the upper surface encapsulant resin
layer 156 is covered with a top plate 158, and the lower surface
encapsulant resin layer 160 is covered by a backing plate 164. In
this embodiment of the present invention, the upper surface
encapsulant resin layer 156 has a decorative pigment 166 dispersed
therein to simulate the appearance of a conventional roofing
shingle.
[0068] FIG. 12 is a schematic, sectional elevational view of
another embodiment of the photovoltaic module 200 of the present
invention. In this embodiment, the photovoltaic module 200 includes
a solar cell stack or photovoltaic element 212 having an upper
surface 215. The solar cell stack 212 is fitted with external
current-collecting electrodes 214 for connecting the photovoltaic
element 212 to an external load (not shown). In this embodiment, an
encapsulant resin layer 216 covers over the upper surface 215 of
the photovoltaic element 212 , and a decorative overlay 226 is
positioned above the upper surface 215 of the photovoltaic element
212, and in particular in this embodiment, outside the encapsulant
resin layer 216. The overlay 226 is substantially transmissive of
near infrared radiation and infrared radiation. In the alternative,
the decorative overlay can be positioned under the encapsulant
resin layer 216 (not shown) or embedded in the encapsulant resin
layer 216 (not shown). Further, the solar stack 212 is encapsulated
on its lower surface by an inner layer 220 of lower surface
encapsulant resin. In addition, the lower surface encapsulant resin
layer 220 is covered by a backing layer 224. In this embodiment of
the present invention, the decorative overlay 226 simulates the
appearance of a conventional roofing tile.
[0069] The decorative overlay can be formed using a conventional
CMYK printing process. Alternatively, specific inks or coating
compositions can be selected for the purpose of better reproducing
a chosen image or design. The decorative overlay can be formed
using a single ink or colored coating composition, or by two or
more inks or colored coating compositions. Preferably, the inks or
coating compositions are selected from materials that are
substantially infrared-transmissive.
[0070] In one aspect of the present invention, the decorative
overlay is discontinuous and includes a first portion which is free
from any coating material ("cutout portion") whatsoever and a
second portion including coating material. The cutout portion can
be maximized consistent with the design objectives of the
decorative overlay in order to minimize any possible reduction in
the electrical output from the photovoltaic elements associated
with the use of the overlay.
[0071] In another aspect of the present invention, the decorative
overlay includes a first portion which is free from any pigment
material ("unpigmented portion") and a second portion including
pigment material. The unpigmented portion can similarly be
maximized consistent with the design objectives of the decorative
overlay in order to minimize any possible reduction in the
electrical output from the photovoltaic elements associated with
the use of the overlay.
[0072] Solar stacks or photovoltaic elements that can be employed
in the improved photovoltaic modules of the present invention can
include one or more semiconductor photoactive layers of any type
known in the art, such as, for example, semiconductor single
crystal silicon layers, non-single crystal semiconductor silicon
layers such as amorphous semiconductor silicon layers,
microcrystalline semiconductor silicon layers, nanocrystalline
semiconductor silicon layers, polycrystalline semiconductor silicon
layers, and compound semiconductor layers. The photoactive
semiconductor silicon layers can be stacked, and the junctions
between the stacked layers can be of the pn-type, the np-type, the
Schottky type, etc. The photoactive layers can include an n-type
silicon layer doped with an electron donor such as phosphorous,
oriented towards incident solar radiation, and a p-type silicon
layer doped with an electron acceptor, such as boron. The
semiconductor stacks can include transparent electrical current
conducting layers formed from electrically conductive semiconductor
materials such as indium oxide, stannic oxide, zinc oxide, titanium
dioxide, cadmium stannate, and the like.
[0073] The present invention can also employ thin film-type
photovoltaic materials, such as multi-junction amorphous silicon
solar cells produced on thin, flexible stainless steel substrates
and available from United Solar Ovonic LLC, Auburn Hills, Mich.,
which can be encapsulated in UV-stabilized polymers such as
ethylene-vinyl acetate copolymers and fluoropolymers such as Tefzel
(ethylene-tetrafluoroethylene) fluoropolymer available from Du Pont
de Nemours. Thin film photovoltaic materials employing organic
semiconductor materials can also be used.
[0074] Resins suitable for use in the present invention for
encapsulating semiconductor photovoltaic elements include ethylene
vinyl acetate copolymer resins, ethylene ethyl acrylate copolymer
resins, ethylene methyl acrylate copolymer resins, polyvinyl
butyral resins, polyurethane resins, fluororesins, and silicone
resins. Resins that are substantially transparent or at least
transmissive to near infrared radiation and to infrared radiation,
such as ethylene vinyl acetate resins, are preferred. The resins
can be employed in the form thermoplastic or thermosetting fluids
applied to a substrate including the photovoltaic materials, as
films applied to the photovoltaic materials, or the like.
[0075] The physical properties of encapsulant resins for use in
preparing the photovoltaic modules of the present invention can be
adjusted by selecting resins having suitable average molecular
weight, suitable molecular weight distributions, suitable degrees
of branching, and suitable levels of crosslinking. Preferably, the
physical properties of the encapsulant resin are chosen to provide
suitable impact resistance, low temperature resistance, high
temperature resistance, environmental stability, and adhesion for
use in encapsulating semiconductor photovoltaic elements in
photovoltaic modules for exterior use.
[0076] The encapsulant resins used in preparing the photovoltaic
modules of the present invention can include suitable amounts,
preferably from about 0.1 to 1.0 percent by weight of the
encapsulant resin, of additives to enhance the ultraviolet
radiation resistance and/or the radiation stabilization of the
encapsulant resin. For example, ultraviolet radiation absorbers
such as benzophenones, benzotriazoles, cyanoacrylates, and
salicylic acid derivatives can be employed, including
2-hydroxy-4-methoxybenzophenone,
2-hydroxy-4-n-octyloxybenzophenone,
2-(2-hydroxy-5-t-octylpheyl)benzotriazole, titanium dioxide, cerium
(IV) oxide, zinc oxide and stannic oxide. Preferred ultraviolet
radiation absorbers include nanoparticle zinc oxides and titanium
dioxides. Suitable radiation stabilizers, which are to be used in
conjunction with ultraviolet radiation absorbents, include hindered
amine bases such as, for example, derivatives of
2,2,6,6-tetramethyl piperidine of lower molecular weight or in
polymeric form. The encapsulant resins can also include
antioxidants such as hindered phenols, and adhesion-promoting
agents such as organic titanates.
[0077] The optional top plate or cover member used for preparing
the photovoltaic modules of the present invention is preferably
formed from a material which is substantially transparent to near
infrared radiation and infrared radiation, and has good mechanical
strength. Suitable materials include tempered glass sheets having
high transparency to near infrared and infrared radiation, and
synthetic polymer sheets and films such as fluororesin sheets and
films, and acrylic sheets and films. Suitable fluororesins include
polyvinylidene fluoride resins and tetrafluoroethylene-ethylene
copolymers. When a synthetic polymer film is employed as a cover
member, the cover member preferably has a thickness of from about
10 to 100 micrometers.
[0078] In some embodiments of the photovoltaic module of the
present invention, the encapsulant resin can include a visible
light-absorbing colorant, such as a dye or pigment. Preferably,
when such a visible light absorbing colorant is included in the
encapsulant resin, the colorant is selected to have high
transmissivity to near infrared radiation and infrared
radiation.
[0079] In the photovoltaic module of the present invention, the
lower surface encapsulant resin may be the same resin as employed
as the upper surface encapsulant resin. However, the lower surface
encapsulant resin can also differ from the resin used as upper
surface encapsulant resin, in that the service requirements differ
for these two resin layers. In particular, the lower surface
encapsulant resin need not be transmissive to near infrared
radiation and infrared radiation. Thus, in addition to the resin
materials that can be employed for forming the upper surface
encapsulant resin layer, other resin materials, such as epoxy
resins, can be used to form the lower surface encapsulant resin
layer.
[0080] The backing plate employed in preparing the photovoltaic
modules of the present invention is preferably formed from a rigid
material, such as aluminum, steel, or a reinforced composite
material, and more preferably a rigid electrically insulating
material having low electrical conductivity, such as a nylon, a
polytetrafluoroethylene material, polycarbonate, polyethylene,
polystyrene, polyester, or the like. However, more flexible, less
rigid materials may also be employed.
[0081] Preferably, in the photovoltaic modules of the present
invention a color layer is selected such that, despite its
pigmentation, it does not prevent the passage of the wavelengths
within the solar spectrum that are largely responsible for the
photovoltaic activity.
[0082] The present invention also provides a method of producing a
photovoltaic module having controllable and desirable aesthetics
for use in roof applications while still maintaining sufficient
efficiency in power generation. In the process of the present
invention an overlay film or coating having a desirable visual
appearance in the visible range of the spectrum, and substantially
transmissive of near infrared and infrared radiation is applied to
or incorporated in a photovoltaic device. The photovoltaic device
is capable of producing electricity because near infrared and
infrared radiation passing through the overlay film or coating
activate the photovoltaic device.
[0083] In one embodiment, the coating or film is transmissive or
transparent in the near infrared range and scatters, reflects or
absorbs light in the visible range of the spectrum to produce a
desired appearance. Infrared-transmissive pigments can be used to
provide visible color to the coating or film. Suitable
infrared-transmissive pigments can be inorganic or organic. In the
case of organic pigments, it is preferred to include a protective
overlay film that contains an ultraviolet absorber. The ultraviolet
absorber provides an element of weatherability enhancement for
organic transparent pigments. Examples of infrared-transmissive
pigments that can be employed in the photovoltaic modules of the
present invention include zinc sulfide, zinc oxide, nanoparticle
titanium dioxide and other nanopigments, CI Pigment Black 31, CI
Pigment Black 32, CI Pigment Red 122, CI Pigment Yellow 13,
perylene pigments, ultramarine blue pigments, quinacrodone
pigments, azo pigments, and pearlescent pigments.
[0084] Preferred polymers for such films include acrylics,
polycarbonates and fluoropolymers such as fluororesins. Ultraviolet
radiation resistant polymers such as acrylic polymers and
fluoropolymers are especially preferred.
[0085] In one embodiment, a continuous coating or film is provided
over the entire surface of the photovoltaic module. In another
embodiment, the coating or film is discontinuous. Such
discontinuous coatings can be applied by printing techniques.
Coloration to produce the desired appearance can be accomplished by
a three- or four-color halftone printing process where different
portions or dots are printed with different colors to provide an
overall visual effect when viewed from a distance. In some
instances, monochromatic prints can also be employed where the base
background color of the photovoltaic module itself also contributes
to the overall color and appearance of the modified module of the
invention.
[0086] In the case of a discontinuous coating, some of the printed
areas can optionally be opaque even to near infrared or infrared
radiation provided a sufficient area of the photovoltaic surface is
available to capture light to activate the device. Such opacity in
selected portions of the surface can be used to expand the range of
accessible aesthetic effects for the photovoltaic module in a
roofing application.
[0087] The use of infrared-transmissive pigments to modify the
surface of photovoltaic modules greatly improves the ability to
harmonize such modules in an aesthetically pleasant fashion with
the rest of the roofing cover while, also eliminating the narrow
color selection issue posed by the products currently
available.
EXAMPLE
[0088] A photovoltaic cell was connected to a Simpson 260 volt
meter and exposed to sky light on a sunny day with an ambient
temperature of 24 C. The voltage reading for the output of the
photovoltaic cell was 8.3 V. The visual appearance of the
photovoltaic cell was unchanged from its natural condition.
[0089] A sheet of infrared long-pass film having a high
transmissivity in the near infrared region of the spectrum and
strong absorbance in the visible spectrum was placed over the
exposed surface of the photovoltaic cell. The voltage reading for
the output of the photovoltaic cell was 7.8 V. The photovoltaic
cell was completely obscured by the infrared long-pass film and the
surface had a black appearance. The electrical output of the
photovoltaic cell remained at 94% of its natural level without the
infrared-transmissive overlay.
[0090] Various modifications can be made in the details of the
various embodiments of the processes and articles of the present
invention, all within the scope and spirit of the invention and
defined by the appended claims.
* * * * *